The present invention relates generally to apparatus for mixing and dispensing multi-component materials, and in particular, to a gun for dispensing a two-component plastic foam wherein spraying and/or mixing are carried out or assisted by pressure from a confined gas. The pressurized gas may be carbon dioxide, or other gas. In the preferred form, the gun is constructed and arranged so as to be suitable for throw-away use, i.e., to form a part of a kit that is able to be discarded when the contents forming a part of the kit are depleted.
In recent years, improvements have been made in dispensing multi-component plastic materials, primarily foams, many of which are urethane foams or those involving similar chemistry. In such foams, an "A" or isocyanate component and a "B" or resin component are mixed adjacent the point of dispensing and the thus-formed mixture reacts in or near the dispensing nozzle or like part of the apparatus. In the past, the combination of the heat from the reaction between the resin and the isocyanate, and the reduced pressure resulting from passage outside a pressurized container would cause a dissolved liquid propellant, such as a halocarbon of low boiling point, to expand and create a froth. Such expansion can also be used to create a propulsive force.
Systems of this sort have been placed in widespread use and have made it possible for a wide variety of users to derive the benefits of on-site generation and dispensing of urethane foam for purposes of insulation, flotation, void fill and the like. Prior to the development of urethane foam systems such as those described in U.S. Pat. Nos. 3,784,110 and 4,676,437, for example, urethane foams were made in factories by non-portable equipment. In some cases, very small, aerosol-can sized quantities were available, but these were too small and expensive for use in commercial construction or industrial applications. The development of the patented systems referred to above enabled urethane foam to be mixed on-site and dispensed from kits that were light enough to be portable by users, and yet large enough to dispense significant quantities of foam. Typically, the kits that are readily portable are capable of mixing and dispensing 100-600 board feet of uniformly high quality urethane foam. Such foam usually has a finished density of 1.5 to 4.5 pounds per cubic foot ("pcf") and provides buoyancy, adhesion structural rigidity and outstanding heat insulation.
However, in the last several years, there has been significant concern with the relatively recently developed belief that the propellants for such dispensing systems are harmful to the environment. It is now widely accepted that many kinds of propellants previously used in urethane foam systems, namely, fluorocarbon propellants, including so-called CFC's, HFC's, HCFC's and other volatile organic compounds ("VOC's") are harmful to the earth's ecology. In one particular, for example, it is believed that fluorocarbons deplete ozone from the upper atmosphere.
Consequently, for reasons of regulatory compliance and environmental concerns generally, alternative propellants have been sought for use with foam systems. While alternate propellant systems are known, including the use of perhaps other halocarbons and carbon dioxide, most or all of these other propellants have suffered from disadvantages and drawbacks of various kinds. In one case, alternate fluorine-containing propellants have been expensive and difficult to obtain in a desirable range of boiling points. Some low molecular weight hydrocarbons are available, but VOC and flammability considerations are a problem.
Some carbon dioxide (CO.sub.2) systems have involved use of the isocyanate in the "A" component to create carbon dioxide, usually by reacting it with water, to create CO.sub.2. This has some advantages if used for foam blowing only, but is relatively wasteful if the expensive isocynate is sought to be used as a propellant. This was one historic reason for developing "Freon" (fluorocarbon) propellants in the first place. Consequently, while the use of CO.sub.2 as a blowing agent and as a propellant is known, making propellant from isocyanate is undesirable.
As a consequence of the foregoing, there has been a need for a dispensing system wherein it would be practical for a suitable gas to be used as a propellant, either wholly or in part, and wherein the contents of two containers of the foam-forming or other compounds could be reliably mixed and dispensed at low cost. There has also been a need for a dispensing gun having an improved valving system, preferably a system wherein the flow of both liquid and gas or vapor phase constituents could be controlled in a desirable way. Such a gun could be used in plants or in portable throwaway applications. There has also been a need for a dispensing gun system wherein it is possible to provide sufficient propellant to insure dispensing of two mixed components of a urethane or like foam through a range of dispensing rates.
There has also been a need for a dispensing spray gun which could be used with inexpensive, throw-away nozzles that would provide a static mixing function for the liquids, and a function for the gas or vapor used to apply the products.
Inasmuch as there is no highly satisfactory disposable multi-component foam dispensing gun and nozzle system able to dispense mixable urethane foam or like ingredients and propel them to the installation site either using economically generated CO.sub.2 as part or all of the propellant, or using another gas source, it is an object of the present invention to provide an improved dispensing system for such foams.
Another object of the present invention is to provide a foam dispensing gun which includes an improved, separable, low-cost, throw-away nozzle for use with such an improved dispensing system.
Another object of the present invention is to provide a spray nozzle that develops a desirable spray pattern using CO.sub.2 or other suitable gas as a propellant.
Yet another object of the invention is to provide a dispensing gun that includes a pair of liquid inlet ports registered through a valve system with a pair of liquid outlet ports, and which further includes gas inlet and outlet ports, with flow of liquid and gas respectively through the ports being controlled by different but commonly operated valving systems.
A further object of the invention is to provide an improved dispensing gun using a single trigger that actuates two kinds of valves, one suitable for liquid metering and the other for metering a gas, a liquid, or other propellant.
A still further object of the invention is to provide a mixing and dispensing system which includes a low-cost dispensing gun and a throw-away nozzle, with the nozzle including a pair of liquid inlet ports, a gas propellant inlet port, a static mixer for the liquids and a discharge area at which the propellant gas impinges upon the liquids being mixed and expanding and serves to propel them from the nozzle inlet.
Another object of the present invention is to provide a nozzle that will use a minimal amount of gas to achieve high liquid shear for mixing and propulsion.
Yet another object of the invention is to provide a mixing and dispensing gun which utilizes a triggering system capable of simultaneously or sequentially operating a propellant valve and a pair of liquid discharge valves.
A further object of the invention is to provide a low cost dispensing system utilizing a dispensing gun having a gas valve arrangement whereby sufficient propellant to expel being-formed foam from a mixing and dispensing nozzle can be provided at various liquid flow rates and wherein the gas flow rate is not directly proportional to the flow of liquid into the mixing nozzle.
A still further object of the invention is to provide a mixing and dispensing system which includes a mixing gun having three inlets and three outlets, and which is adapted for use with a nozzle that confines the being-mixed chemicals to its interior and which also provides an annular liquid discharge and propellant impingement area within the product outlet nozzle.
Another object of the invention is to provide a dispensing gun which includes pairs of inlet and outlet passages for liquid components and a spool valve having passages movable into and out of full and partial registry with such ports to control liquid flow, and which also includes a gas flow valve, with both the spool valve and the gas valve being actuable by a single trigger.
Yet another object of the invention is to provide a gas dispensing system which includes a gas valve having a passage of major and minor diameters, a valve core with counterpart major and minor diameters, and an interior passage arrangement whereby axial movement of the stem permits gas flow through the minor diameter passage and into the mixing and discharge nozzle.
It is still another object of the present invention is to provide a dispensing gun for foam products wherein the gas valve stem is carried by a yoke secured to one portion of a trigger which also actuates the liquid flow valves.
A still further object of the invention is to provide an arrangement of valves and a trigger including a spool valve having ears on both ends actuable by a bifurcated trigger and further including a gas valve having a reciprocable core with stepped diameters, with the core being carried by a yoke mechanism that is also connected to the trigger.
Another object of the invention is to provide a gun wherein the valve core or stem for the air passage includes a hose connection secured to the valve core and arranged such that the hose and valve core move together and whereby the only primary gas seal is between registered parts of the valve passage and the valve core.
Yet another object of the invention is to provide a number of the foregoing features in a combination which further includes a latching and ejector mechanism for a replaceable nozzle and which includes other desirable elements including a reliable trigger spring return and trigger safety assembly.
Still another object of the invention is to provide a combination of two types of valves for liquid and gas, respectively, each operating on a different principle, but being actuated by a single trigger.
A further object of the invention is to provide a gun wherein the valves open at different times but are operable by a single trigger.
The foregoing and other objects and advantages of the invention are achieved in practice by providing a dispensing gun that includes a handle, an assembly for receiving a removable together with a trigger unit that actuates liquid and gas valves, respectively including a spool valve and a reciprocable valve core, with all valves being positioned within passages for receiving liquid or gas constituents and each communicating with an inlet on the nozzle. The invention also achieves these and other of its objects by providing such a gun made from low cost, but reliable materials.
The manner in which the foregoing and other objects and advantages are achieved in practice will become more clearly apparent when reference is made to the following detailed description of the preferred embodiment of the invention set forth by way of example and shown in the accompanying drawings, wherein like reference numbers indicate corresponding parts throughout.